Alzheimer's is a progressive brain disorder that affects memory, thinking, and behavior. It is the most common cause of dementia, a general term for a decline in cognitive function. Symptoms often start with mild memory loss and can eventually lead to severe impairment in daily activities. The exact cause of Alzheimer's is not fully understood, but it involves the buildup of proteins in the brain, leading to cell death. Risk factors include age, family history, and certain genetic markers. While there is currently no cure, treatments are available to help manage symptoms and improve quality of life.